Method for producing guerbet alcohols

ABSTRACT

The invention relates to a method for producing Guerbet alcohols of formula (I), CH 3 (CH 2 ) n CHR 1 CH 2 OH, wherein R 1  represents a linear alkyl radical having n−1 carbon atoms, and n represents 3 to 9 carbon atoms. Fatty alcohols of formula (II), R 2 OH, wherein R 2  represents linear alkyl radicals having 6 to 12 carbon atoms, are condensed in the presence of carbonyl compounds and alkali hydroxides.

FIELD OF THE INVENTION

[0001] The invention relates to the field of cosmetic oil bodies orcomponents and concerns an improved method for producing Guerbetalcohols without the use of heavy metal catalysts.

STATE OF THE ART

[0002] Guerbet alcohols represent primary alcohols which are branched inthe 2-position and which are obtained by the condensation of linearfatty alcohols. The products are used predominantly as oil componentsfor the production of cosmetic emulsions. The basic starting point forthe production thereof is generally fatty alcohols which in a first stepundergo self-condensation under the influence of strong bases and heavymetal compounds such as for example copper or zinc oxide. It is assumedthat, under the reaction conditions, the alcohol is firstly dehydratedto form the aldehyde, the latter reacting with itself in an aldolcondensation and the condensation product is then hydrated to form thealcohol. An overview in that respect is to be found for example inAngew. Chem. 64, 212 (1952).

[0003] There is, however, the disadvantage that the heavy metalcatalysts have to be separated off again after the reaction isterminated in order to satisfy statutory requirements and to ensure thatthey do not cause irritations in the later use. Separation is generallyeffected by washing with subsequent distillation, in which respect thelatter involves not inconsiderable product losses.

[0004] Accordingly the object of the present invention is to provide amethod of producing Guerbet alcohols which, compared to the state of theart, operates more economically and with reduced environmentalpollution. In particular, the invention seeks to avoid the use of heavymetal catalysts and simple distillative purification of the productsshould be guaranteed without expensive centrifugal washing.

DESCRIPTION OF THE INVENTION

[0005] The subject-matter of the invention is a method of producingGuerbet alcohols of the formula (I)

CH₃(CH₂)_(n)CHR¹CH₂OH   (I)

[0006] wherein R¹ represents a linear alkyl radical having n−1 carbonatoms and n represents numbers of between 3 and 9 carbon atoms, whereinfatty alcohols of the formula (II)

R²OH   (II)

[0007] wherein R² represents linear alkyl radicals having between 6 and12 carbon atoms are condensed in the presence of carbonyl compounds andalkali metal hydroxides.

[0008] It was surprisingly found that carbonyl compounds, especiallyfatty aldehydes, as alternatives to heavy metal compounds, alsorepresent suitable catalysts for the Guerbet reaction, in particular ifthey are added at high temperatures. Accordingly a particular advantageof the method is that the condensation reaction is effected, withcomparable levels of yield, in the absence of heavy metals, no washingis required in the finishing operation and thus there are also no longerany product losses.

[0009] Fatty Alcohols

[0010] Fatty alcohols, preferably those of the formula (I) in which R²represents an alkyl radical having between 8 and 10 carbon atoms aresuitable for the condensation operation. Typical examples are hexanol,octanol, decanol, dodecanol and mixtures thereof.

[0011] Carbonyl Compounds

[0012] The carbonyl compounds which are used as catalysts are ketones,and in particular fatty aldehydes which are preferably in accordancewith the formula (III)

R³CHO   (III)

[0013] wherein R³ represents linear alkyl radicals having between 6 and12 and in particular between 8 and 12 carbon atoms. Typical examples arehexanal, octanal, decanal, dodecanal and mixtures thereof. It has provento be particularly advantageous to use fatty alcohols and fattyaldehydes with the same alkyl radical. Usually the carbonyl compounds ingeneral and the fatty aldehydes in particular are used in amounts ofbetween 0.2 and 50, preferably between 1 and 25 and in particularbetween 3 and 10 mol %, with respect to the fatty alcohols.

[0014] Condensation

[0015] The condensation reaction can be performed in per se knownmanner, that is to say the fatty alcohols, together with the bases, areheated to temperatures in the range of between 200 and 250, preferablybetween 210 and 240° C. The carbonyl compounds can then be added at atemperature of between 20 and 250° C. to the mixture of fatty alcoholsand alkali metal hydroxide. It has proven to be advantageous, however,for the addition operation to be implemented at higher temperatures,that is to say between 210 and 240° C. The speed of addition also has aninfluence on the condensation reaction. Typical times are times ofbetween 0.1 and 10 hours, having regard to the reaction speed and theyields, however, the recommendation is between 10 and 60 minutes. Theamount of alkali metal hydroxides can be between 1 and 10, preferablybetween 3 and 5 mol % with respect to the fatty alcohols. Preferably atleast 40% by weight of sodium hydroxide or in particular potassiumhydroxide lye is used. At any event, to displace the reactionequilibrium onto the product side it is recommended that thecondensation water be continuously distilled off. As organic material iseasily entrained in that case it has proven worthwhile to use adephlegmator, by means of which the organic phase is separated off andcan be recycled into the starting material. The work-up procedure whichnow manages without a washing step then involves simple distillation.This affords fewer product losses and a lower level of waste waterpollution.

EXAMPLES

[0016] Example 1. 1000 g (6.3 moles) of decanol (95% by weight) was putin a stirring apparatus comprising a flask, a heating-mantle member, adephlegmator, a Liebig condenser, a nitrogen transfer device and adouble-stroke piston pump, mixed at 20° C. with 22.5 g (0.22 mol) of 45%by weight potassium hydroxide solution and heated to 215° C. The waterwhich occurred upon heating was continuously distilled off. Then 29.6(corresponding to 3 mol % with respect to decanol) was meteredly addedby way of the pump within 60 minutes and in that operation thetemperature raised to 240° C. The distilled organic phase was fed to thereaction mixture after phase separation. The reaction was terminatedafter 6 hours. A GC analysis of the product mixture showed that 76% byweight of 2-octyidodecanol was produced; in addition the reactionmixture contained 6% by weight of trimers, 14% by weight of unreactedmonomer alcohol and 4% by weight of mixed Guerbet alcohols consisting ofC₁₈- and C₂₂-Guerbet alcohols. Purification of the product was effecteddistillatively, the unreacted decanol was removed as a first running andwas reintroduced into the reaction mixture; the residue that remainedwas the higher-molecular constituents.

[0017] Example 2. Similarly to Example 1 1000 g (6.3 mol) of decanol wasmixed with 22.5 (0.22 mol) of potassium hydroxide solution and 29.6 g ofdecanal and heated to 240° C. The water produced in the heatingoperation was continuously distilled off and the distilled organic phasefed to the reaction mixture after phase separation. The reaction wasterminated after 6 hours. A GC analysis of the product mixture showedthat 43% by weight of 2-octyidodecanol was produced; in addition thereaction mixture contained 2% by weight of trimers, 53% by weight ofunreacted monomer alcohol and 2% by weight of mixed Guerbet alcoholsconsisting of C₁₈- and C₂₂-Guerbet alcohols.

1. A method for producing Guerbet alcohols of the formula (I)CH₃(CH₂)_(n)CHR¹CH₂OH   (I) wherein R²represents a linear alkyl radicalhaving n−1carbon atoms and n represents numbers of between 3 and 9carbon atoms, wherein fatty alcohols of the formula (II) R²OH   (II)wherein r² represents linear alkyl radicals having between 6 and 12carbon atoms are condensed in the presence of carbonyl compounds andalkali metal hydroxides:
 2. A method as set forth in claim 1characterized in that fatty alcohols of the formula (I) in which R²represents an alkyl radical having between 8 and 10 carbon atoms areused.
 3. A method as set forth in claim 1 and/or claim 2 characterizedin that fatty aldehydes are used as the carbonyl compounds.
 4. A methodas set forth in at least one of claims 1 to 3 characterized by usingfatty aldehydes of the formula (III) R³CHO   (III) wherein R³ representslinear alkyl radicals having between 6 and 12 carbon atoms.
 5. A methodas set forth in at least one of claims 1 to 4 characterized in that thecarbonyl compounds are used in amounts of between 0.2 and 50 mol % withrespect to the fatty alcohols.
 6. A method as set forth in at least oneof claims 1 to 5 characterized in that the carbonyl compounds aremeteredly added to the mixture of fatty alcohols and alkali metalhydroxide at a temperature of between 20 and 250° C.
 7. A method as setforth in at least one of claims 1 to 6 characterized in that thecarbonyl compounds are meteredly added within between 0.1 and 10 hours.8. A method as set forth in at least one of claims 1 to 7 characterizedin that the alkali metal hydroxides are used in amounts of between 1 and10 mol % with respect to the fatty alcohols.
 9. A method as set forth inat least one of claims 1 to 8 characterized in that the condensationproducts are subsequently purified by distillation.
 10. A method as setforth in at least one of claims 1 to 9 characterized in that thecondensation operation is performed in the absence of heavy metalcatalysts.